A new wireless load monitoring system is in use at an Oxford construction site to provide real-time measurement of forces on basement props.
Temporary works specialist Mabey is using its new LIVEpin load monitoring system for the first time to monitor prop loads at the 85m x 300m basement propping scheme for the £500m Westgate Centre redevelopment.
Laing O’Rouke is the project’s main contractor for Crown Estates and Land Securities.
Sitting in the place of the shear pin that anchors a prop, Mabey’s LIVEpin technology comprises a data-enabled shear pin that measures the axial load on the prop, communicating wirelessly with on-site dataloggers that save and retransmit the data. Readings are transmitted every 30 minutes.
Although LIVEpin was not specified for this project, Mabey opted to install LIVEpins on two out of the 114 props it has supporting the excavation.
The system allows for the setting of load thresholds which, when exceeded, trigger a switch to a 60-second reporting cycle to enable fine-grained analysis and recording. Once loads drop below the preset threshold, the reporting cycle is reset to every 30 minutes. The dataloggers on site store the data and simultaneously upload it to the Mabey LIVEsite web portal for real-time monitoring and analysis.
Mabey engineering director Dave Holland explained: “We wanted to be able to ascertain the load in a strut using the most accurate method possible. By locating the gauges in the shear pin at the end of the strut, we have achieved an exceptionally high accuracy of ±2% under concentric and eccentric loads and at varying temperatures and magnitudes. Redundancy is built into the system, so the LIVEpin and the dataloggers store data as well as transmitting it, meaning that no data is lost in the event of a network or wireless outage.”
Mabey’s LIVEpin is the latest addition to its range of LIVE instrumentation products, which includes environmental monitoring, geodetic and geotechnic monitoring, and temperature monitoring, all integrated into Mabey’s LIVEsite web portal.
